Combination gas and oil burner and control therefor



c. c. YOUNG COMBINATION GAS AND 011. BURNER AND CONTROL THEREFOR Filed Sept. 1, 1948 April 3, 1951 3 Sheets-Sheet 1 f2: Veazzfczz" 6: 12! CZ'Yazzzzg I I 7 4 5 R 2 m m L m T N 0 C m .R E m B L I O D N A S A G N O I T N m m C C. C. YOUNG April 3, 1951 3 Sheets-Sheet 2 Filed Sept. 1, 1948 NM QM www (L, m

April 3, 1951 c. c. YOUNG 5 7,6

COMBINATJQON GAS AND OIL BURNER AND CONTROL THEREFOR Filed Sept. 1, 1948 I5 Sheets-Sheet 3 JZZV'EZQTZZLUI" 63/121 675 5124? Patented Apr. 3, 1951 UNITED STATES PATENT OFFICE COMBINATION 'GAS AND OIL BURNER AND CONTROL THEREFOR Cyril Charles Young, :Kansas'City, Mo.

. .Applicationseptember 1, 1948, Serial No. 47,319

.18 Claims. '1 This invention relates to a combination oil and gas burner unit particularly adapted for domestic or industrial heating purposes.

In my copending applications, Serial Nos.

764,697 and 764,698, filed July "30, 1947, there is disclosed and claimed a novel combination gas and oil burner unit and "control system therefor which will permit a heating plant to be elliciently operated either by an oil fuel or by a gas fuel, such as is derived from the ordinary city gas main. This type of burner unit has the advantage that for moderate outdoor temperatures, the heating of "the building or residence in which the unit is installed may be accomplished solely by a gas fuel. However, upon the occurrence of extreme weather conditions, the unit may be operated to burn the oil fuel and adequately supply the required amount of heat without constituting an excessive demand upon the city gas supply. Under present day conditions wherein the supply of gas is necessarily limited due to the overwhelming demand therefor, such a combined unit has very remarkable advantages from the standpoint of reducing the peak load requirements of a city gas system.

Specifically, this application relates to certain improvements both in the burner construction and the control therefor over the arrangements disclosed in my above identified copending applications. One feature of this invention is the incorporation of an air blower in the burner unit to supply a pressured stream of air to support the combustion of the oil fuel. In accordance with this invention, such pressured stream of air is conveniently supplied through the same conduit that supplies the combustible gas and air mixture for the main burner gas "flame.

Still another feature of this invention is the provision of an improved control arrangement for a combination gas and oil burner unit characterized by the incorporation therein of certain interlocking circuits between the valves cont-rolling the supply of oil and gas fuel to the burner unit, to insure that under no conditions of operation will both the main gas burner and the oil burner be in concurrent operation, which would tend to produce an excessive heating of the furnace unit so as to involve the possibility of damage thereto.

This improved control circuit also includes inter'locking arrangements for insuring that the blower which supplies a stream of pressured air to support the combustion'of the oil fuel through the same conduit as the combustible gas and air mixture for the main gas burner name is supplied, will not be operated at any time when the burner is operating on the gas cycle, furthermore, to insure that such blower will be in operation at all times when'the burner is operated on the oil cycle, and lastly, to insure the shut down of the burner in the event that a failure of the blower motor occurs while the burner is operating on the oil cycle.

Accordingly, it is an object of this invention to provide an improved combination gas and oil burner and control circuit therefor.

Another object of this invention is to provide an unusually simplified arrangement for supplying a stream of pressured air to a combination on and gas burner to support the combustion of oil fuel therein and characterized by the utilizathan of a common conduit for such air stream and for the combustible gas and air mixture when the burner is operating on its gas cycle.

Still another object of this invention is to provide an improved control system for a combination oil and gas burner which will insure that the burner will never be operated with both fuels being supplied thereto concurrently, and further more, to effect the shutdown of the unit in the event of the failure of any of the essential components thereof, such as the pilot flame or the blower for supplying the pressured air stream to support the combustion of the oil fuel.

The specific nature of this invention, as well as other objects and advantages thereof will become apparent to those skilled in the art from the following detailed description of the annexed sheet of drawings which by way of preferred example only, illustrate on specific embodiment of the invention.

On the drawings:

Figure 1 is a vertical sectional view of the combustion chamber portions of a combination gas and oil burner constructed in accordance with this invention;

Figure 2 is a vertical sectional view of the remaining portions of the combination gas and oil burner unit, showingparticularly the arran gements for supplying main burner gas, vaporizer gas, and a stream of pressured air to the combustion chamber assemblage illustrated in Figure -1.; and

Figure 3 is a schematic diagram of the electrical control system for a combination gas and oil burner.

As shown on the drawings:

As indicated above, this application constitutes certain improvements over the burner construction and control circuits disclosed in my above referred to copending applications. Accordingly, the unmodified elements of the burner unit will not again be described in detail and reference should be had to my copending applications for a detailed description of all elements of the burner unit which have not been modified in accordance with this invention.

The numeral I indicates the combustion chamber of a furnace which is supported in a relatively elevated position on a hollow cylindrical casing 2. All of the combustion producing elements of the combination gas and oil burner unit embodying this invention may then be convenently mounted within the confines of the casing 2 in generally symmetrical relationship with respect to the vertical axis of a fire box opening Ia provided in the bottom of the fire box or combustion chamber I of the furnace.

The combination burner unit embodies a base casting ll! of generally inverted, cup-shaped configuration having an annular base portion I l and a depending cylindrical wall portion I2 integrally formed on the periphery of base portion l I. At spaced intervals around the periphery of wall portion l2, a plurality of supporting leg portions l3 are provided, each of which is further provided with a radially extending flange I l. The top surface of each of the flanges is is provided with a pair of circumferentially extending arcuate grooves l5 and [6 respectively, which are radially spaced from each other. Thus the groove 16 is formed on the peripheral edge of the flanges M, while the groove i5 is formed in an intermediate portion of the flanges M.

Base portion H of base casting is has a flared juncture with an integral, upstanding cylindrical hub portion H which defines a central bore I 8. Within the bore IS a vertical, tubular gas burning conduit or nozzle member 19 is positioned. The nozzle member i9 is of cylindrical exterior configuration and fits snugly within the hub por tion within the bore if of hub portion ll. At its bottom portions, the nozzle member it] connects with a horizontal conduit 2!! which extends radially outwardly of the ca ing 2 to a vertical wall 4 and there connects with the discharge port 2111 (Figure 2) of a blower housing 2|. A sleeve 22 is inserted in the horizontal conduit 2 and the bore of such sleeve defines a Venturi nozzle 22a. A motor driven blower rotor 21b is disposed in conventional fashion within the blower housing 2| and, when the electrical motor 48 (Figure 3) driving the blower rotor 2Ib i energized, the rotor will operate to pump a pressured stream of air into nozzle 22a, hence through conduit 20 and nozzle member 19, and thus produce an upwardly directed air stream directed toward the combustion chamber I to support the combustion of vaporized oil fuel in a manner that will be described in more detail later.

In accordance with this invention, the conduit 20 is also employed to conduct a combustible mixture of gas and air to the vertical nozzle m mber l9 to supply the main burner gas flame when the combination burner unit is operated on its gas cycle. Such combustible mixture of gas and air may be produced by a conventional inspirator nozzle 23 which projects into the blower housing 2| at a point ad acent the outlet port 21a thereof. Gas is supplied to inspirator nozzle 23 through a conventional electrically operated valve unit 24 which in turn is connected to a gas main 25.

Adjacent to the central nozzle member I9, a conventional pilot flame unit 26 is provided which is indicated in dotted lines in Figure 1. Also, a pilot flame thermal switch unit 21 of conventional construction is mounted adjacent to the pilot flame unit 26 and operates in conventional fashion to maintain a pair of switch contact closed so long as the pilot flame is burning and to open such contacts in the event of failure of the pilot flame produced by the pilot flame unit 26. Pilot flame unit 25 is supplied with gas through a pipe 26a which connects to the gas main 25 at any desired point.

The innermost groove 15 provided in the radial flanges M of the base casting It supports a generally cylindrical shell 30 which is mounted thereon in upstanding relation. An annular gas burner element 3| of generally hollow, toruslike configuration is mounted on the top of shell 30 and in surrounding relationship to the upstanding hub portion l'! of the base casting l9, hence in surrounding relationship to the mouth of the upstanding nozzle member i9. Burner element 3! is provided with two axially spaced sets of a plurality of gas burner jets 32 extending around its inner periphery and respectively directed angularly upwardly and downwardly toward the axis of the base casting is. Each of the jets 32 communicates with the hollow bore 33 of the gas burner element 3! and a supply pipe 3A provides a combustible mixture of gas and air to the hollow portion 33. Supply pipe 3A. in turn connects with a mixing nozzle 28 mounted on wall 4 (Figure 2) and gas is supplied to the mixing nozzle 28 by a conventional jet 28 which is connected to the gas main 25 through a pipe 29a and an electrically operated valve 18. When the valve 10 is in its open position, two axially spaced rings of gas flames are produced by the torus-like burner element 3!, which will hereafter be referred to as the vaporizer burner.

Vaporizer burner 3| is further provided with a radially inwardly extending ledge 35 extending around its inner circumference. A ring 35a of heat insulating material rests upon such ledge and, in turn, is utilized to support an annular vaporizing pan or tray 36, which has an outturned edge 31 engaging the ring 35a. Vaporizing tray 36 may be of any desired configuration and preferably is provided with a depressed base portion 38a so as to permit a substantial quantity of fuel oil to be collected in the vaporizer tray without danger of spilling therefrom. It will be noted that the tray 36 is thus supported intermediate the two rings of flame produced by the vaporizer burner 3i, and hence the tray will be rapidly heated to a high temperature. The insulating ring 35a sealingly mounts the tray 36 without substantial transfer of heat from the hot vaporizer tray to the relatively cool vaporizer burner.

To further amplify the heating effects of the gas jets of the vaporizer burner 3|, a pair of refractory rings 38 and 39 are respectively mounted in axially spaced relationship below and above the vaporizer tray 36. Thus the bottom refractory ring 38 may be conveniently supported upon the top surface of the base portion II of the base casting Ill.

The upper refractory element 39 is supported in depending relationship from an annular support plate or cover 40, which in turn rests upon the base portion 42 of an inverted, generally cup-shaped housing 4|. Housing d! is in turn supported in the peripheral groove [6 in the radial flanges M of the base casting E0. The plate so defines an inverted annular trough 44 which surrounds a central aperture 4.5 which is generally concentric with the axis of the base casting Ill. Therefractory elements arose-cured to the cover plate All in any convenient manner, such as :is described in detail my copending applications vSerial Nos. 754,697 and 716%,698, filed July 30, I19l'7. To further facilitate the heatin of the vaporizer tray 36, the opposed surfaces of refractory el ments 3.8 and 13.9 are preferably provided with a plurality of spaced refractory points 55. V

The cover plate 40 is provided with an aperture is which is alignable with an aperture is in the pper refractory elements as. Hence a passage is provided through plate ill and refractory element .39 directly overlying the vaporizing tray 36, and this passage is employed to supply a limited flow of fuel oil to the vaporizin tray 36 when it is desiredto bur-n fuel oil in the .combined burner unit.

A drip type nozzle 53 is positioned directly above the aperture 49 and is connected to :a suitable source of fuel oil through va pipe 51 and an electrically operated valve 4! (Figure 2).. To protect the drip nozzle 59 from the high temperatures developed within the burner unit and .to effect the feeding of the fuel oil to the vaporizing tray 36 without carbonization, the nozzle and the supply pipe 5i are preferably encased within a sheet metal conduit 54 which extends to wall 4 and is open to atmosphere so as to permit a flow of cooling air to continuously inducted through such conduit. Such conduit .54 not only provid additional air for combustion of the gas and oil within the burner, 12

.but also effectively maintains the drip nozzle .50 .at a sufficiently low temperature that carbonizetion of fuel oil thereon is prevented. Conduit .54 is supported by a clamp 55 011 an upstanding integral pedestal .56 formed on the cup-shaped housin 4 I.

From the foregoing description, it is apparent that whenever fuel oil is supplied to the vaporizing tray 35 through the energization of valve 42 to its open position, such fuel oil will 'be rapidly evaporated due to the high temperature of the tray and its location within the high temperature zone between the refractory elements 38 and 39. If the blower motor as is concurrently energized, a large volume stream of air will be produced which passes upwardly through the central opening in the annular vaporizer tray .35 and provides adequate air to support the combustion of the vaporized fuel oil. :The temperature of the vaporizing zone is maintained su-fficlently high to insure the rapid vaporization of fuel oil supplied thereto and, while some cracking of fuel oil occurs, any resulting combustibles are completely consumed, due to the high temperature of the vaporization zone and the presence of adeq ate oxy en.- any ash or non-combustibles depo ited in the tray 36 are also swept into the air stream by the induced air flow produced around both the upper and lower faces of the'burner tray '36. Hence it is assured that the vaporizer tray remains clean.

To effect an intimate mixture of the fuel oil vapors and the combustion supporting air stream, a mixing nozzle to is provided of generally Venturi configuration. Nozzle to is supported by a plurality of radially extending arms til upon nuts 62, which are in turn adiustabl-y positioned on threaded studs .63 mounted'in upstanding rela tionship on the .base portion of the inverted cupshaped housing M. Hence the axial position of 6 .the,;mi-xer :nozzle to with respect to the opening 4:5 the vaporizer cover all maybe conveniently adjusted. Furthermore, it should be noted that nozzle to is axial-1y spaced with respect to the plate as and is also of smaller diameter than the firebox openmg In, so that additional flow of combustion supporting air into the combustion chamber is permitted by the resulting opening.

When the unit is properly adjusted and the optimum axial position of nozzle determined, a thorough mixing action of :fuel oil vapors and combustion supportin air occurs in the throat of the nozzle 60 and the burning of the com bustible mixture is initiated before the mixture passes .out of the end of the nozzle and :into the combustion chamber 1. Preferably a target or flame spreader .3 is mounted in chamber 1 in conventional fashion.

The aforedescribed arrangement permits high .efficiency combustion to be obtained when the burner unit is operating on either its gas or oil cycle. 'The pilot flame produced by the pilot flame unit '23 is, of course, always in operation.

When operating'on the gas cycle, the motor 4.8 is deenergized and the :valves ll and Ill which respectively control the flow of oil to the vaporizing tray and the flow of gas to the vaporizer burner '3l are closed. Gas "is supplied through the main gas valve 24 and adequate amounts of air necessary to support combustion are supplied by natural draft through the burner unit. "When operating on the oil cycle, the main :gas valve 2 3 :is actuated to its closed position and the .oil valve in and the vaporizer gas valve 1.0 are :act11 .ated to their open position and the blower :rotor 21b is rotated.

Referring now to Figure 13., there is disclosed a control circuit embodying this invention for selectively controlling .the energization vof the main gas valve 24, vaporizer gas valve 1.0, oil valve t1, and blower motor 43.. :It is, of course, to be understood that the initiation of operation .of the burner unit .on either its gas burning or oil burning cycle may be automatically controlled in any desired manner and the particular arrangement for cycle selection shown in Figure :3 corresponds identically to that disclosed in my above referred to copending application Serial No. 7 64;698 wherein the selection of the gas or oil burning cycle is controlled by an outdoor thermostat i! and the intermittent operation of the burner on the selected cycle is controlled by a room thermostat '52. The control circuit may be operated from any suitable source of power indicated as line terminals Li and L2 and, if such source is of .the alternating current type, may be stepped down to a suitable voltage by transformer '13.

The .outdoor thermostat .II is preferably of the snap action type wherein the switch blade lid of the thermostat selectively engages either the contact G or a contact 0 depending upon whether or not the outside temperature is vabove or below a predetermined value. For purposes of illustration, it will be assumed that the outdoor thermostat it will have its switch blade Ila bridged across its neutral terminal N to the terminal G. for all outdoor temperatures above a predetermined value and will have the switch blade Ha bridged across the neutral terminal N and the terminal 0 for .all outdoor temperatures below such a predetermined value. The shifting of the switch blade Ha between the terminal and the terminal 0 then effects the operation of the burner uni-t respectively on its gas and its oil burning cycles in a manner to be described.

The indoor thermostat 12 may be of any conventional type and has been illustrated as of the well known three wire type, including a. heating element 121) and a pair of contacts 12a which are closed whenever the room temperature is below a predetermined value and are opened whenever the room temperature exceeds a predetermined value.

The vaporizer gas valve may be of any conventional electrically operated construction and for illustrative purposes is shown as a solenoid controlled type.

Main gas valve 24 is an electrically operated valve controlled by a conventional solenoid unit. Associated with main gas valve 24 is a circuit interlocking arrangement comprising a pair of contacts 24a and an actuator means cooperating with the stem of the main gas valve 24. When main gas valve 24 is closed, contacts 24a are closed and the control circuit to oil valve 41 is complete. But, regardless of how main gas valve 24 is opened, whether it be opened automatically by electrical means, manually or whether it be jammed open because of mechanical failure, the actuator means will operate to open contacts 2401, thereby breaking the electrical control circuit to oil valve 41. This safety feature precludes simultaneous entry of the two different fuel media into the burner unit.

The oil valve 41 preferably incorporates a conventional delay action or time lag device so as to impart a suitable time delay characteristic in its operation, i. e., it will not initiate the flow of fuel oil to the burner unit until a substantial predetermined interval after its original energization and conversely, will continue to supply fuel oil to the burner unit for a limited period after its deenergization. Electrically operated fuel oil valve 41 may constitute any one of several well known forms and for illustrative purposes has been shown as comprising a heater type valve including an electrical heater 41a, which is the electrically energized element of the valve, and a time lag device which in this embodiment includes a bimetallic element 412) which operates an actuating bar 410 when heated by the heater element 41 a. Actuating bar 41c cooperates with a pair of interlocking switches 14 and 15 and the stem 41d of the fuel oil valve 41 to actuate such elements in a predetermined sequence, both upon the energization of the fuel oil valve 41 and upon the deenergization thereof. As schematically indicatedin Figure 3, the desired sequence of operation is that a short time after the original energization of heater element 41a, the actuating bar 410 effects the opening of the contacts of switch 14 and the closing of the contacts of switch 15. After a still further time interval, the actuating bar 410 engages the stem 41d of the valve to open the valve to permit fuel oil to be supplied to the burner unit. Upon deenergization of the heater element 41a, the sequence of operation is reversed. The valve stem 4101 is first released to its closed position and then after a predetermined time delay, the switch 15 is actuated to its open contact position while the switch 14 is actuated to its closed contact position.

Referring particularly to that portion of the circuit represented by the heavy black lines of Figure 3, it will be seen that the vaporizer valve 1i! and the blower motor 48 are concurrently energized by the closing of the normally open contacts of the switch 15 subsequent to the energization of the heater coil 41a of the electrically operated oil valve 41. Hence, it is assured that the vaporizer gas valve 16 will be opened and supplying gas to the vaporizer burner 3| to heat the vaporizer tray 36 to suitable temperature and that the blower 2 lb will operate before any fuel oil is supplied through the valve 41 to the vaporizing tray 36. The time delay in corporated in the mechanism of the electrically operated oil valve 41 insures that oil will not be supplied to the vaporizing tray 36 until proper combustion conditions are attained.

At the same time the opening of the contacts of the normally closed switch 14, which will be seen to be connected in the energization circuit of the main gas valve 24 insures that the main gas valve 24 will remain deenergized and thus in its closed position. Accordingly, irrespective of other conditions in the circuit, the main gas valve 24 cannot be opened when the fuel oil valve 41 has been energized.

It should be further noted that if oil valve 41 is operated manually, as might well occur under operating conditions subsequent to an electrical current interruption, or if oil valve 41 is jammed open because of mechanical difficulties, valve stem 41d operates to open switch 14 thereby breaking the electrical control circuit to main gas valve 24. Inasmuch as the contacts 24a, which are associated with the main gas valve 24, are connected in series circuit with the heater elements 41a of the electrically operated fuel oil valve 41, the electrical control circuit between the fuel oil valve 51 and the main gas valve 24 is completely interlocked so irrespective of how one of the valves may have been opened, simultaneous operation by electrical means of both main gas valve 24 and oil valve 41 is precluded.

Normally closed contacts of a safety switch unit 16 associated with the blower 2|b are also connected in the energizing circuit of the heater element 41a of the electrically operated valve 41. The switch 16 is of well known construction and is associated with the blower rotor 2|b in such manner that so long as the blower rotor 2|b is functioning normally, the contacts of switch 16 will remain closed. However, when a failure of the blower rotor 2|b occurs, the switch 1% will open and result in the deenergization of the heater coil 41a of the fuel oil valve 41 and hence a closing of the fuel oil valve 41. In addition, contacts of the pilot flame responsive switch 21 are connected in the common lead 11 which is included in the energizing circuits of both the fuel oil valve 41 and the main gas valve 24. Accordingly, upon the failure of the pilot flame, the pilot flame switch 21 will open its contacts and prevent the operation of either the fuel oil valve 41 or the main gas valve 24.

The cooperation of the outdoor thermostat 1| and the indoor thermostat 12 with the remaining elements of the control circuit is identical to that employed in my above referred to copending applications. When the outdoor temperatures are below a predetermined value, circuit connections are completed as illustrated in Figure 3 through the terminal 0 of the outdoor thermostat 1| to energize the heater element 41a of the electrically operated fuel oil valve 41 whenever the indoor thermostat 12 is calling for heat by closing of its contacts. When the outdoor temperature is above such predetermined value the outdoor thermostat 1| completes an energization circuit through its contact G for the main gas valve 24 whereby only oil'or only whenever the indoor thermostat 2 calls-for heat by the closing of its contacts 12a.

.From the foregoing description, it is apparent that this invention provides not onlyan improved and simplified construction of .a combined gas and oil burner unit through the utilization of a commonconduit for the supply of the pressured air stream for 'theburner while operating on the oil cycle and for the supply of the combustible mixture of gasandair when operating-en the gas cycle, .but the-described controlcircuitcompletely prevents the concurrent supply :of both :main bnrnergas and fuel .oil .to the burner unit minder any conditions of operation. Furthe1 more, the interlocking of the gas andoil valves with the pilot flame switch and the blower protector switch insures that fuel :will notice supplied to the burner unit :unless proper combustion conditionsare first produced inthe burner unit.

It will, of course, be understoodthat various details of construction .may be modified through a :wide range withouthdeparting from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

Iclaim as my invention:

1. A control system for .a combined-gas and oil burning heater comprising, in combination, a first electrically operated valvemeanscontrolling the supply of gas to said heaten-a second electricallyoperated valve means controlling the supply-of oil to said heater, a thermostat a-nd circuit means controlled by said thermostat for selectively energizing said first-or secondvalve means, said circuit means including a pair of interlocking switches respectively operated'to open positionby energization of said first-and second valve means, means connecting the interlocking switch operated by said first valvemeans in circuit with said second valve means, and means connecting the'interlocking switch operated by said second valve mean-sin circuit with said firstvalvemeans, gas'may be suppliedto said heater. I

2. A control system for apembined-gas and ,oil burning heater comprising, in combination, a first electrically'operated valve-means ccntrolling the supply ofgas to-said heater,a second electrically operated *valve means controlling the supply of'oil to saidheater, a'thermostat, andcircuit means controlled by said thermostat 'for selectively energizing said first orjsecond"valvemeans, said circuit means including switch means associated with each of said "first and second valve means and actuatablethereby "for interlocking the energization circuit of said first and second valve means to prevent concurrent energization of both valve means, whereby only oil or onlygas may be supplied to said heater at any onetime.

3. In combination, ;a gas and voil .lourning heater, a first electrically operated valve means controlling the supply of gas "to said heater, ,a second electrically operated valve means controllingthe supply of oil to saidheater, a third electrically operated valve-meansffor controlling the supplyof an'oil vaporizing medium "to said heater, a thermostat, circuit-means controlled by said thermostat for selectively energizing either said first valve meansor said second and-third valve means .concurrently, said circuit means including a pair of interlocking switches respectively operable .toopen :position by energization of said first and second valve means, .means connecting the:interlockingswitch:operated by said first valve means in circuit withsaid secondwalve means, and .mea-ns connecting the interlocking switch operated by said second valve means in circuit with said first valve means, whereby only oiior only gas may be supplied to said-heater at any onetime.

4. -A;.control.system fora combined gas and oil burning heater comprising, in combination, --a firstelectricallyoperated valve means controlling the :supply of-gas-to said heater, -a second electricallyoperated valve means controlling the supply of :oil tosaid heater, a thermostat and circuit means controlled .by said thermostat ior selectively energizing said first-or second valve means, an electrically operated blower arranged to produce a stream of air to support thecom- .bustion of the .oil, switch means responsive '-to operation :of said second valve means forenergizing said blower, and switch means actuatable in response to operation of said first and second valve :means for interlocking the energization circuits of said firstand second valve means to prevent concurrent energization of both valve means, whereby only oil or only gas may be supplied to said heater at any one time.

5. In combination a gas andoil burning :heater,

a firstelectrically operated valve means controllin the supply of gas to said heater, a second electrically operated valve means co-ntrollingthe supply of oil .to .said heater, a third electrically operated valve meanscontrolli-ng the supply of anoilvaporizing medium to said heater, an electrically driven blower arranged to produce a stream of air to support combustion-of the oil, a thermostat, circuit means controlled by said thermostat i'orselectively energizing either said first valve means or said second valve means, and switch means associated with said second valve :means for energizing-bothsaid third valve means and saidblower when said second valve means is energized.

6.11m combination a gas and oil burnin heater, a first electrically operated valve means controlling the supplyof gas to said heater, -a second electrically operated valve m'eans controlling the supply of-oil --to said heater, a third electrically operated valve means controlling the supply of an .oil vaporizing medium to said heater, an electrically driven blower arranged to produce a stream of air to support combustion of the oil, a thermostat, circuit means controlled by said thermostat for selectively energizing eithersaid first valve means or said second valve means, and .switch means associated with said second valve. means for energizing both said third valve means and said blower when said second valve means is energized, a pair of interlocking switches respectively operated to open position by energization .of said first and second valve means, means connecting the interlockingswitchoperated'by said first valve means in circuit with said second valve means, and means connecting the interlockingswitch operated by said second valve means in circuit with said first valvemeans, whereby only oil or only gas may be suppliedto said heater at-any one time.

'7. In combination, a gas and oil burningheater, afirst electrically operated valve means controllingthe supply of gas to said heater, a second electrically operated valve means controlling the supply of oil to said heater, a third electrically operated'valve meanscontrollin the supply of an :oil vaporizing medium to said heater, an electrically driven blower arranged to produce a stream'of air to support combustion of the oil,

a thermostat, circuit means controlled by said thermostat for selectively energizing either said first valve means or said second valve means, and switch means associated with said second valve means for energizing both said third valve means and said blower 'When said second valve means is energized, and switch means responsive to operation of either said first or second valve means for interlocking the energization circuits of said first and second valve means to prevent concurrent energization of both valve means.

8. In combination, a heater having means for burning a gas fuel and vaporizing means for burning an oil fuel, a first electrically operated valve means controlling the supply of' gas to said heater, a second electrically operated valve means for controlling the supply of oil to said heater, said second electrically operated valve means including means for delaying opening and closing movements of the valve in response to energization and deenergization respectively, a third electrically operated valve means for controlling the supply of gas for heating said vaporizing means, an electrically driven blower, switch means associated with said second valve means for energizing said third valve means and said blower subsequent to the energization of said second valve means but preceding the opening of said second valve means to supply oil to said heater, a thermostat, and circuit means controlled by said thermostat to seletcively energize either said first valve means or said second valve means.

9. In combination, a heater having means for burning a gas fuel and vaporizing means for burning an oil fuel, a first electrically operated valve means controlling the supply of gas to said heater, a second electrically operated valve means for controlling the supply of oil to said heater, said second electrically operated valve means including means for delaying opening and closing movements of the valve in response to energization and deenergization respectively, a third electrically operated valve means for controlling the supply of gas for heating said vaporizing means, an electrically driven blower, switch mean associated with said second valve means for energizing said third valve means and said blower subsequent to the energization of said second valve means but preceding the opening of said second valve means to supply oil to said heater, a thermostat, and circuit means controlled by said thermostat to selectively energize said first valve means or said second valve means, and means for interlocking the energization circuits of said first and second valve means to prevent concurrent energization of both valve means.

10. In combination, a heater having means for burning a gas fuel and vaporizing means for burning an oil fuel, a first electrically operated valve means controlling the supply of gas to said heater, a second electrically operated valve means for controlling the supply of oil to said heater, said second electrically operated valve means including means for delaying opening and closing movements of the valve in response to energization and deenergization respectively, a third electrically operated valve means for controlling the supply of gas for heating said vaporizing means, an electrically driven blower, switch means associated with said second valve means for energizing said third valve means and said blower subsequent to the energization of said second valve means but preceding the opening of said second valve means to supply oil to said heater, a thermostat, and circuit means controlled by said thermostat to selectively energize either said first valve means or said second valve means, a pair of interlocking switches respectively operated to open position by energization of said first and second valve means, means connecting the interlocking switch operated by said first valve means in circuit with said second valve means, means connecting the interlocking switch operated by said second valve means in circuit with said first valve means, thereby preventing concurrent operation of said first and second valve means.

11. The combination defined in claim 8 plus means for producin a pilot flame, and wherein said circuit means includes a normally closed switch operable to open contact position upon failure of said pilot flame, thereby cutting on all fuel supply to said heater.

12. The combination defined in claim 9 plus means for producing a pilot flame, and wherein said circuit means includes a normally closed switch operable to open contact position upon failure of said pilot fiame, thereby cutting off all fuel supply to said heater.

13. The combination defined in claim 8 wherein said circuit means includes a normally closed switch operable to open contact position upon failure of said blower, thereby interrupting all fuel supply to said heater.

14. The combination defined in claim 9 wherein said circuit means includes a normally closed switch operable to open contact position upon failure of said blower, thereby interrupting all fuel supply to said heater.

15. The combination defined in claim 8 plus means for producing a pilot flame, and a pair of normally closed switch devices series connected in said circuit means, one of said switch devices being operable to open contact position by failure of said pilot flame and the other of said switch devices being operable to open contact position upon failure of said blower, thereby interrupting the supply of fuel to said burner upon operation of said switch devices.

16. A gas or oil burning heater comprising an annular vaporizing tray, means including a first valve for supplying oil to said tray, means for maintaining said tray at a vaporizing temperature, a gas burning nozzle arranged to project a gas fiame through the central opening of said vaporizing tray, a conduit connected to said nozzle, a blower operatively connected to the other end of said conduit to produce an air stream discharge from said gas burning nozzle, means including a second valve for injecting a stream of gas into said conduit, and means for energizing said blower only when said first valve means is operated to supply oil to the heater.

1'7. A control system for a combined gas and oil burning heater comprising, in combination, a first electrically operated valve means controlling the supply of gas to said heater, a second electrically operated valve means controlling the supply of oil to said heater, a thermostat, an electric circuit controlled by said thermostat, means within said circuit responsive to said thermostat to selectively actuate said first and second valve means, said circuit means including a pair of interlocking switches, each being respectively operable to an open position whenever either one of said first and second valve means is in an open position, and additional circuit means associated with said pair of interlocking switches for respectively interconnecting said switches in circuit between said first and second valve means whereby when either of said first and second valve means is in an open position the other of said first and second valve means cannot be energized to an open position.

18. In combination, a gas and oil burning heater, a first electrically operated valve means controlling the supply of gas to said heater, a second electrically operated valve means controlling the supply oil to said heater, a third electrically operated valve means controlling the supply of gas to an oil atomizer burner within said heater, a thermostat, circuit means controlled by said thermostat for selectively energizing either said first valve means or said second and third valve means concurrently, sai-d circuit means including a pair of interlocking switches respectively operable to open position when either of said first and second valve. means is opened, means respectively interconnecting said interlocking switches and said first and second valve means in circuit, whereby only gas may be supto said heater concurrently with the gas being supplied to said oil atomizer burner at any time.

CYRIL CHARLES YOUNG.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,786,901 Doherty Dec. 30, 1930 1,840,744 Scott Jan. 12, 1932 1,860,311 Klees May 24, 1932 1,885,478 Powers Nov. 1, 1932 1,995,846 Gauger Mar. 26, 1935 2,064,914 Heinzel Dec. 22, 1936 2,168,680 Nordgren Aug. 8, 1939 2,313,340 Harris Mar. 9, 1943 2,370,172 Kaufman Feb. 27, 1945 

